Field of the Invention
The present invention relates to a gas sensor element, a gas sensor, and a method for manufacturing the gas sensor element.
Description of Related Art
Gas sensors are used for combustion control of internal combustion engines. A gas sensor includes a gas sensor element that outputs, as a detection signal, the concentration of a specific component (e.g., oxygen) in an exhaust gas from an internal combustion engine. For example, a gas sensor element disclosed in Patent Document 1 includes an alumina sheet having a through-hole penetrating therethrough in the thickness direction, and the through-hole is filled with a zirconia filling portion having oxygen ion conductivity. A pair of electrodes are provided on both surfaces of the zirconia filling portion. Patent Document 1 discloses a structure in which the thickness of the zirconia filling portion is larger than the depth of the through-hole (i.e., the thickness of the alumina sheet) so that the zirconia filling portion projects from the through-hole, and the size of the projected part of the zirconia filling portion is larger than the opening area of the through-hole.